Purpose: The purpose of this study was to evaluate a new method for the detection of Salmonella in cocoa product based on a single enrichment in skimmed milk followed by a DNA extraction with a purification solution formulated to neutralize the effect of the inhibitory components and a subsequent PCR assay with the iQ-Check® Salmonella kit.
Methods: Salmonella stressed strains (heating, 56°C and dehydration, freeze-drying) were used to spike 250 g or 375 g of cocoa containing samples. The spiking levels were below 10 CFU/sample. Spiked samples and control samples were then analyzed in duplicate by the alternative and the standard method including a pre-enrichment in BPW supplemented with dry milk and brilliant green, enrichment in MKTTn and RVS broths and streaking on agar plates.
Results: All the non-spiked samples were negative. A total of 40 spiked samples (high cocoa and low cocoa contents) were tested. All the samples were detected with both, the reference and the alternative methods. The samples treated with the purification solution gave positive results while the non-treated samples showed inhibition of the PCR assays.
Significance: These data show that the new method can be used to detect Salmonella in large size samples of cocoa containing product. The enrichment step can be made in skimmed milk which reduces the cost of the enrichment compared to the reference method. The purification solution allows the use of the PCR based iQ-Check® Salmonella kit, thus improving also the time-to-result.